A known hybrid vehicle includes an internal combustion engine and an electric motor serving as a power source and appropriately converts the driving torques generated therefrom so as to be supplied to a drive-train depending on a traveling status. In the hybrid vehicle, heat is generated when the electric motor drives or is driven for regeneration, and the efficiency of the electric motor is degraded due to the generated heat. To handle such generated heat, the size of the electric motor is increased, or the electric motor is cooled by water-cooling using an installed water jacket or by oil-cooling using an oil pump for pressurizing a lubricant (cooling oil) of a transmission so as to be effected to the electric motor (for example, see PTL 1). PTL1 discloses the motor controller and the control method thereof for ensuring the flow rate of the lubricant at a low-temperature at which the viscosity of the lubricant increases. When the temperature of the lubricant is a predetermined temperature or less, the lubricant is heated by controlling a voltage and a current supplied to the electric motor so as to increase the loss of the electric motor.